The present invention is related to switching systems and is more particularly concerned with a novel totally optical switching system for communication purposes in which modulated beams of light are selectively switched between a plurality of inputs and a plurality of outputs.
The use of "light" frequency electromagnetic energy for communication purposes has recently been brought much closer to reality through the production of extremely low loss optical fibers and the extension of continous wave (CW) room temperature operation of diode lasers to over ten thousand hours. The new optical fibers exhibit only 2 db of loss per kilometer.
As a result of the foregoing developments, it is becoming increasingly apparent that the greatest loss in such a communication system occurs at those positions within the system where conversion between electrical and optical signals is required. At least with respect to known techniques for converting electrical signals to optical signals, definite limitations in conversion efficiencies are a fact of life. One particular portion of the system where such conversion efficiencies are extremely detrimental is in the switching networks. Presently, most such switching networks are exclusively electrical and require conversion from the optical signals to electrical signals before application to the network and subsequent reconversion to optical signals after the signal leaves the switching network.
Optical switching tree systems have been suggested. In such systems, an incoming light beam is deflected into one of two directions by a deflector. Each of the alternate beam positions are then passed to a second level of similar deflectors thereby producing four possible beams. N successive stages of such deflection produce 2.sup.N beams. If M total beams are required to enter the systems, each of these must be treated separately by M such deflector trees before being accorded entry into appropriate outgoing optical fiber waveguides.
U.S. Pat. No. 3,871,743 to Fulenwider describes an optical crosspoint switching matrix for an optical communication system. This system is essentially an optical equivalent of an electrical crosspoint switching matrix. It utilizes a large number of separate acoustooptic beam steering mechanisms to switch light beams from a planar waveguide into an optical fiber waveguide and vice versa. Such a system includes a large number of fiber to waveguide coupling arrangements thereby greatly increasing the cost and complexity of the system.